LeetCode Online Judge-389. Find the Difference

Given two strings s and t which consist of only lowercase letters.

String t is generated by random shuffling string s and then add one more letter at a random position.

Find the letter that was added in t.

Example:

Input:
s = "abcd"
t = "abcde"

Output:
e

Explanation:
'e' is the letter that was added.

//Java Program: Find the Difference
public class Solution {
    public char findTheDifference(String s, String t) {
        ArrayList<Character> alC = new ArrayList<Character>();
        for(int i=0;i<s.length();++i) {
            alC.add((Character)s.charAt(i));
        }
        for(int i=0;i<t.length();++i) {
        if (!alC.remove((Character)t.charAt(i))) {
                return t.charAt(i);
            }
        }
        return t.charAt(0);
    }
}